A. An enumeration district (ED for short) is an administrative division of a particular county or township for the purposes of census-taking. Each census taker would be assigned one or more EDs, each of which was designated with a number.

At one time, to find your ancestor's census return, you’d have to identify which roll of census microfilm contained the right ED. Now that US censuses have been indexed by name, people don’t have to identify EDs the way they used to.

But you may find EDs handy for a few reasons:

If you can’t find a household in records for a database site such as Ancestry.com, you can browse by ED (in Ancestry.com, choose a census year, then scroll below the search box to pick a state, county or township; a ward; then an ED).

Enumerators didn't always proceed through their EDs in orderly
fashion: Rather than go down one side of the street and up the other,
they might cross back and forth or double back to places where
no one was home. But you can compare a census return to a map of the
corresponding ED to plot the neighborhood and see who lived next to
your relatives.

When the 1940 census comes out in 2012, a name index won't be available right away—but while you wait, you'll be able to find your ancestors' records using the ED.

To identify your ancestor's enumeration district, you’ll need to know the state, city and street name, and possibly a street number. Then, try these tools:

Stephen P. Morse’s website has ED finding tools for the 1900 to 1940 censuses. Start by reading this overview to see which ED-finding tool you need (the 1940 tutorial quiz asks you a series of questions that will lead you to the ancestor's ED).

Morse’s site also offers tools for ED number conversions between 1920 and 1930 censuses, and 1930 and 1940.

NARA has put ED information for each census on microfilm. Series A3378 has ED maps for 1900 through 1940; series T1224 has descriptions for 1830 through 1890, and 1910 through 1950. T1210 has ED text descriptions for the 1900 census.

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